A large eddy simulation study of Arctic boundary-layer cloud during ASCOS

A number of recent studies in both the central Arctic and along the north coast of Alaska have observed the intrusion of stratocumulus cloud top well into the capping temperature inversion – a feature that is not seen at lower latitudes. The processes governing the extension of cloud into the inversion are not clear, but it has been suggested that they are linked to the observation of humidity inversions in the Arctic, in which specific humidity increases above the boundary layer and cloud top – another unusual feature of the Arctic environment.

Here we present some results of large eddy simulations of Arctic stratus, based upon, and compared with observations from the ASCOS project made in the central Arctic during summer 2008. The extension of cloud top into the temperature inversion is found to arise naturally in the simulations in the presence of a humidity inversion. The impact of this process on the mean and turbulent structure of the cloud is examined and compared with in situ and cloud radar measurements from ASCOS. Some of the sensitivities to environmental conditions are also considered.